Refactoring class hierarchy. Moving Caso to Event::Handler.

1. Using multiple inheritance in Button for InputPin dependency.
2. Adding direction handling in Canvas/ST7735R. Updating example.
3. Improving IOStream.print for buffers. Adding max print per line.
4. Updating all classes that inherit Cosa. Changed to Event::Handler.
5. Using multiple inheritance in ST7735R. Adding inheritance from SPI::Driver.
6. Improving CosaCanvasSweep example.